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The Satellite - SSETI-Express
The satellite and its mission in short
SSETI-Express is a so called "Micro-satellite", its dimensions are
60x60x80cm and it weighs in at 62kg which is 1kg heavier than the
Danish Ørsted
satellite, which was launched in 1999. The SSETI-Express project
started in January 2004 and peaks with its launch on the 27th of
September 2005. This short schedule makes it the fastest developed
micro-satellite mission in history! The satellite has been built by students from 14 different universities across Europe. The project has been supervised by the European Space Agency (ESA). The students have been organised in 12 different teams which has cooperated during the project. Coordination has happened using the Internet as a tool for meeting, discussion and information sharing. The satellite has been integrated and tested at the European Space Technology and Test Centre (ESTEC) in Holland, where the students have been working during short stays.
As part of its mission SSETI-Express carries into orbit three small "passenger satellites" each weighing a kilo. These are built by students from Norway, Germany and Japan respectively. These passenger will be deployed 74 minutes after SSETI-Express has been put in orbit.
SSETI-Express and its passengers will reach orbit with the help of a Russian "Cosmos-3M" launcher and will share the launch with the "Disaster Monitor Constellation 3" from Surrey Satellite Technology Limited (SSTL). The orbit will be circular and sun synchronous with an altitude of 686km.
Mission Objectives
The SSETI-Express mission has the following mission objectives:• To demonstrate that a distributed student group can carry out a micro-satellite project
• To deploy three cubesat passengers
• To take pictures of the Earth
• To perform technical experiments with student built hardware in space
• To function as a radio-relay for radio amateurs worldwide
Also see the SSETI-Express mission pages for more information or the SEOR page on SSETI-Express for a concise technical description
Description of contributions from students from Aalborg University
The following paragrpahs provides descriptions of the subsytems that students from Aalborg university have contributed with.The On-Board Computer and Software
| With Karl in the lead the group has developed the micro-computer which are situated in the midst of the spider-web of wires that connects the on-board systems of SSETI-Express. The computer, and the software that the group has developed for it, controls everything the satellite does and stores all the generated data from the on-board instruments, so that they can be downloaded to ground. |
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As the computer is a central piece of the satellite jig-zaw then Karl
has been in Holland many times during the project in order to help
other teams interface to the computer and make corrections to the
on-board software.
For the same reason Karl is also one of the project participants that knows the satellite best. Therefore he is also chosen to be on the team that travels to Plesetsk in Russia in order to perform the final preparations and checkout of the satellite. Karl says about the time leading to launch: "Now we are waiting to see if we have built something that can survive the launch and the space tough space environment. SSETI-Express can do it, just wait and see!". The group graduated in the summer 2005 as master candidates in "Intelligent Autonomous Systems" and Karl has continued his studies as a master student. |
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Attitude Determination and Control System
| The satellite cannot point in a random direction! For example its antenna should point towards the Earth when it flies over the groundstation. This task has been solved by Lars. He has been involved with the project since its start as whispers in the corridors of ESTEC. The Task has been solved using a combination of permanent magnets and electromagnetic coils, which interacts with the magnetic field of the Earth. In addition to controlling the attitude it is also necessary to actually know which way the satellite is pointing this is done using sensors that measures the direction of the magnetic field of the Earth relative to the satellite and the direction to the sun relative to the satellite. |
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In addition to the ACDS task then Lars has also been helping the
"systems engineering team", which are responsible for the overall
design of the satellite. Here he has performed advanced
multi-disciplinary simulations of the on-board systems in order to
estimate how they will cooperate in space. Finally he will be
responsible for coordinating the operation of the satellite during
the first few critical days following launch until the launch
campaign team returns from Russia.
"To design a satellite is a creative, multi-disciplinary and multicultural process, and it is very far from the conception that some have about 'Space nerds'. And then it is great fun!" says Lars. Lars graduated in the summer of 2004 with a master in "Intelligent Autonomous Systems" and has hereafter been a PhD student at Aalborg university where he studies advanced autonomy concepts for future space missions. He was also involved with the AAU-cubesat satellite launched in 2003. |
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Camera System
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An important part of the payload of the satellite is the digital
camera which has been developed at Aalborg University in close
coorporation with the local company
Devitech . The camera will
be used to take pictures of northern europe and give the students and
other interested people a small view at how our planet looks from
space.
Originally the camera was not build for the Express satellite but instead for the much smaller AAU Cubesat which is a 1kg 10x10x10 cm size satellite which was built at Aalborg University and launched 2 years ago. However the camera was never tested and it was decided to make a severely modified version which could be used on Express which Morten has been working on. |
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The camera is a 1280x1024 (1.3 Mpixel) colour camrea with a small zoom
lens that enables it to take pictures of the earth which measures
about 400x300 km. This measn that it cannot take pitures of your
backyard or peoples license-plates as may knows it from Hollywood
movies.
"As a study project the task of building a satellite is close to ideal, but it is also very demanding. When the satellite has been launched it is flying around 600 km about us you cannot just go tighten that small but very very important screw some one had forgotten needed tightening. If you for get that or one of a 1000 other small things everything has been futile". Morten graduated as Master of Science in "Intelligente Autonome Systemer" in the summer 2004 and was thereafter employed at Aalborg University as a PhD student where he works with autonomous helicopters which will be used for mine-detection. He was very much involved in the AAU Cubesat project. |
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Groundstation in Aalborg and at Svalbard
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There is not much point in having satellite that one cannot
communicate with. Therefore the group has developed a groundstation
consisting off antenna, dish, radio and computers for controlling
it. The primary groundstation is placed on the roof of Aalborg
university where it has a good view towards space. In addition to the station in Aalborg then the group has also cooperated with a professional groundstation at Svalbard in Norway. Here high north the conditions for communicating with satellite are especially good. Some of the equipment at Svalbard has been modified in in order to make it compatible with the SSETI-Express mission. The work on the groundstations has offered the opportunity to work with radio-amateurs from around the world. Kresten, who is become a bit of radio-amateur himself, says: "It's a very giving experience to cooperate at an international level on a project like SSETI-Express. One get to know many exciting people and shares many good times with them". The group is currently in their last year of studies. |
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Mission Control Centre Software
| In order to be able to command the satellite and display its status, the group has developed a piece of software that acts as "command console" for the satellite. It operates on top of the groundstations. |
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The software is also responsible for safely archiving the data that
are downloaded from the satellite in a database, such that they can
be used for later analysis. The software makes use of both the
groundstations in Aalborg and at Svalbard.
Their software consists of a server part and a client part. The server runs on a computer at Aalborg university, while the client can be run from any computer in the world that has a web-browser. Martin Green says: "The most exciting experience that I have had with SSETI-Express was when I has to travel to Svalbard in order to agree with the experts there how our software could interconnect to their network". The group is currently in their last year of studies. Martin and Martin will spend the autumn semester as interns at ESTEC in Holland where they will work on satellite formation control. Rasmus will spend the semester at Stanford University in California where he will study in their micro-satellite department. Kristian and Axel will be in Canada where they will work on "Discrete Event Systems" with application to satellite radio communication. |
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